Android ndk（cmake）：在第二個jni庫中使用log api時，對__android_log_write的未定義引用

Question

我使用Android Studio 2.2和cmake構建jni文件。

我想在jni文件中顯示日志，但收到錯誤消息“對__android_log_write的未定義引用”。

我的CMakeLists.txt文件是：

add_library( # Sets the name of the library.
         native-lib

         # Sets the library as a shared library.
         SHARED

         # Provides a relative path to your source file(s).
         # Associated headers in the same location as their source
         # file are automatically included.
         src/main/cpp/native-lib.cpp )

add_library( # Sets the name of the library.
         test-lib

         # Sets the library as a shared library.
         SHARED

         # Provides a relative path to your source file(s).
         # Associated headers in the same location as their source
         # file are automatically included.
         src/main/cpp/test-lib.cpp )

include_directories( src/main/jni/ )

# Searches for a specified prebuilt library and stores the path as a
# variable. Because system libraries are included in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.

find_library( # Sets the name of the path variable.
          log-lib

          # Specifies the name of the NDK library that
          # you want CMake to locate.
          log )

# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in the
# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
                   test-lib
                   native-lib
                   # Links the target library to the log library
                   # included in the NDK.
                   ${log-lib} )

我的兩個jni文件與以下相同，但沒有函數名稱

JNIEXPORT jstring JNICALL Java_com_cyweemotion_www_jnitest_MainActivity_stringFromJNI
    (JNIEnv *env, jobject){
    __android_log_write(ANDROID_LOG_ERROR, "Tag", "Error here");
    std::string hello = "Hello from C++";
    return env->NewStringUTF(hello.c_str());
};

我的build.gradle（Module：app）是

    android {
    compileSdkVersion 23
    buildToolsVersion "24.0.3"
    defaultConfig {
        minSdkVersion 19
        targetSdkVersion 24
        versionCode 2
        versionName '1.02'
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags ""
            }
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            signingConfig signingConfigs.config
        }
        debug {
            jniDebuggable false
        }
    }
    externalNativeBuild {
        cmake {
            path "CMakeLists.txt"
        }
    }
    productFlavors {
    }
}

根據android文檔：將C和C ++代碼添加到您的項目中 。 我想我可以使用log api。

我的代碼或設置有什么問題？

---

更新：

我發現在我的第一個jni庫中沒有問題（更新代碼）。

它僅在第二個庫中發生錯誤。

例如：target_link_libraries（test-lib， native-lib ，...），native-lib是要加載的第二個庫。

因此，native-lib無法使用log api。

現在我唯一能做的就是刪除native-lib。 但是我真的很想知道為什么嗎？

Answer 1

我終於發現我應該分開做鏈接。

target_link_libraries( # Specifies the target library.
                   test-lib
                   native-lib
                   # Links the target library to the log library
                   # included in the NDK.
                   ${log-lib} )

target_link_libraries( # Specifies the target library.
                   native-lib
                   # Links the target library to the log library
                   # included in the NDK.
                   ${log-lib} )